Locals at a farm where the shots were fired said people took cover in basements to shield themselves from the shelling, Russia's RIA Novosti news agency reported.
"This is, of course, a disgrace, people could have died. This is the height of the planting season and there are a lot of people at the farm," Tatyana Kostaryova, a spokeswoman for the local administration, told the agency.
'Metal hail'
Yury Mikhailov, the head of the farm, said most of the shrapnel fell on rooftops and greenhouses.
"Was it frightening? That's not the word for it. It was a metal hail. People took cover in basements," he said.
Russian naval forces said a small anti-submarine vessel from the Baltic Fleet made the mistake during exercises in the Gulf of Finland.
Igor Lebedev, a regional military prosecutor, said the ship was conducting target practice and that some shells or rounds fell on houses near the village.
Russia's Interfax news agency said up to 14 shells from the ship may have landed off-target.
The country's navy has been plagued by a series of mishaps since the collapse of the Soviet Union, including the Kursk submarine disaster in 2000, in which 118 sailors died.